Fig. 1. (Color online) Experimental setup of the CVD growth of monolayer WS₂ sample.

Fig. 2. (Color online) The characterization of monolayer WS₂. (a) Optical image of a monolayer WS₂. (b) Schematics of Raman modes of E_2g¹ and A_1g. (c) Raman spectra of monolayer WS₂ sample. (d) PL spectra of monolayer WS₂ sample. (e) AFM image of monolayer WS₂ sample. (f) Height image intensity profile along the black line in (e).

Fig. 3. (Color online) Pressure-induced Raman vibration in monolayer WS₂. (a) Evolution of the Raman spectrum with pressure for monolayer WS₂ sample. (b) Raman vibrations of monolayer WS₂ as a function of pressure.

Fig. 4. (Color online) (a) Evolution of the PL spectra of monolayer WS₂ sample with pressures. (b) PL peaks of monolayer WS₂ as a function of pressure.

Fig. 5. (Color online) (a) Schematic of material structure and TA measurements of monolayer WS₂ in the DAC. (b) Evolution of TA spectra of monolayer WS₂ under pressure from 0.30 to 3.25 Gpa. (c) A exciton peaks as a function of pressures.

Fig. 6. (Color online) The transient absorption signals of monolayer WS₂ with different pressures: (a) 0.55 GPa; (b) 0.89 Gpa; (c) 1.22 Gpa; (d) 1.56 GPa; (e) 1.89 GPa; (f) 2.23 Gpa; (g) 2.56 Gpa; (h) 2.91 GPa. The red lines are fitting.

Fig. 7. (Color online) The time constants (a) τ₁ and (b) τ₂ of A exciton as a function of pressure.